A Scramjet plugin that emulates the chrome.* extension APIs inside proxied frames, so Chrome extensions (Vencord-style userscripts, ad blockers, etc.) can run against sites loaded through Scramjet. Originally forked from carbonicality/amethyst; this version is a full TypeScript rewrite built directly around Scramjet's plugin API instead of a standalone postMessage-bridged iframe runtime, and ships no UI of its own — it's a library, the host app builds whatever extension-manager UI it wants on top.

Architecture

• Sapphire (src/sapphire.ts) — orchestrator owning installed-extension state (IndexedDB-backed), background contexts, and content-script registrations. Create one per app.
• SapphireContentScriptPlugin (src/SapphirePlugin.ts) — a Scramjet ManagedPlugin. Create one per Frame (matching Scramjet's own convention, see @mercuryworkshop/scramjet-controller's createFrame({ plugins: [...] })), passing it the shared Sapphire instance and that frame's tab id.
• chromeApi.ts — builds a live chrome.*/browser.* object directly on the target realm's real Window (obtained from Scramjet's frame.hooks.init.pre context). No postMessage bridge: addListener captures real function references from that realm, so dispatch is a direct call, not a serialized round-trip. This fixes real bugs the old amethyst design had (e.g. chrome.runtime.getManifest() returning undefined because it was silently async under the hood) and removes a class of injection-timing races.
• Background pages/scripts/service-workers all run in one persistent, invisible iframe per extension (not tied to any tab's lifecycle) — a deliberate simplification over spec-faithful Worker-based MV3 semantics; see the doc comment in background.ts.
• dnr.ts exports a pure checkDeclarativeNetRequest() matcher; it is not wired into Scramjet's fetch path (that hook is undocumented/unstable — see project notes), so wire it into your own request routing if you want extension-driven blocking.

Usage

import { Sapphire, SapphireContentScriptPlugin } from "@x8r/sapphire";

const sapphire = new Sapphire({
  host: {
    getTabId: (win) => /* map a proxied window back to your tab id */,
    getTab: (id) => /* { id, windowId, url, title, active } */,
    getAllTabs: () => /* TabInfo[] */,
    getTabWindow: (id) => /* live Window for tabs.executeScript/cookies.* */,
    navigateTab: (id, url) => /* your router */,
  },
});
await sapphire.init(); // loads previously-installed extensions

// per tab, when creating its Scramjet frame:
controller.createFrame(iframeEl, {
  plugins: [new SapphireContentScriptPlugin(sapphire, tabId)],
});

// installing an extension (host owns the file picker / drag-drop UI):
const extId = await sapphire.installExtension(await file.arrayBuffer(), file.name);